1. Field of the Invention
The present invention relates generally to medical devices designed to come into contact with body tissue and, more particularly, to medical devices which have been rendered bacteriostatic/bactericidal and a process for making them so.
2. The Prior Art
As known, infections, such as nosocomial infections (infections originating in a hospital), result from polymeric, metallic and/or ceramic implanted devices, including external fixation devices, indwelling urological catheters and the like, being placed in the body. Most medical device manufacturers have shied away from employing bacteriostatic compounds as antimicrobial agents in such indwelling devices because of the difficulties associated with producing an adherent, long lasting film on such polymeric, metallic and/or ceramic surfaces.
Heretofore, efforts directed at fighting infection associated with the use of implanted devices tended to reduce their biocompatibility. The balancing of these two goals has been one of the challenges facing the medical practitioner.
In related co-pending applications, all assigned to a common assignee, Spire Corporation, Bedford, Massachusetts, and having at least one common co-inventor, there are disclosed and claimed efforts directed at the dry-coating metallization of polymeric implants to improve their biocompatibility and to reduce phlebitis and infection, and to provide bacteriostatic/bactericidal coatings on implants, both by ion-beam-assisted deposition (IBAD), see Ser. No. 07/663,361, filed Mar. 1, 1991, Mohammed Farivar and Piran Sioshansi, entitled "Metallized Polymeric Implants, Methods and Apparatus," and Ser. No. 07/780,275, filed Oct. 18, 1991, Piran Sioshansi et al, entitled "Bactericidal Coatings for Implants." The disclosures of both of said applications Ser. Nos. 07/663,361 and 07/780,275 are incorporated herein by reference.
Another co-pending application, Ser. No. 07/728,098, filed Jul. 10, 1991, also assigned to said common assignee, Spire Corporation, Bedford, Mass. and having one common co-inventor, discloses an ion implantation process designed to alter silicone rubber's surface to that being characterized by low friction, being hydrocompatible, inkable, deformable, antithrombotic and more wear resistant.
The use of ion beam processing is well known and is widespread. The common assignee herein, Spire Corporation of Bedford, Massachusetts, is one of the pioneers in the field of ion beam technology. A plasma-supported ion beam technique for coating industrial cutting tools with a thin layer of cubic boron nitride to improve the tools' cutting properties is disclosed in U.S. Pat. No. 4,440,108, of Roger G. Little et al, granted Apr. 3, 1984, and assigned to said Spire Corporation. A plasma-ion deposition process of large-grain, thin semiconductor films directly on low-cost amorphous substrates is disclosed in U.S. Pat. No. 4,443,488, also of Roger G. Little et al, granted Apr. 17, 1984 and assigned to said Spire Corporation. A process of preventing surface discoloration in titanium orthopaedic implants by ion implantation is disclosed in U.S. Pat. No. 4,693,760 of Piran Sioshansi, granted Sep. 15, 1987 and assigned to said Spire Corporation. An ion implantation process for plastics to enhance their surface hardness and their resistance to chemical attack is disclosed in U.S. Pat. No. 4,743,493 of Piran Sioshansi et al, granted May 10, 1988 and assigned to said Spire Corporation. A process for passivating the electrochemically active surface of metal alloys so as to inhibit their corrosion is disclosed in U.S. Pat. No. 4,743,308 of Piran Sioshansi et al, granted May 10, 1988 and assigned to said Spire Corporation. A sputter-enhanced ion implantation process, primarily of ball bearings, without the use of a separate evaporation system is disclosed in U.S. Pat. No. 4,855,026 of Piran Sioshansi, granted Aug. 8, 1989 and assigned to said Spire Corporation. An improved method and apparatus for the uniform ion implantation of spherical surfaces, such as ball bearings, is disclosed in U.S. Pat. No. 4,872,922 of Stephen N. Bunker et al, granted Oct. 10, 1989 and assigned to said Spire Corporation. A method of depositing an ionized cluster on a substrate is disclosed in U.S. Pat. No. 4,152,478 of Toshinori Takagi, granted May 1, 1979. And a method of coating a substrate with a stoichiometric compound is disclosed in U.S. Pat. No. 4,281,029 of Toshinori Takagi et al, granted Jul. 28, 1981.